Migration of hydrogen isotopes in lithium metatitanate

Migration mechanisms of hydrogen isotopes in Li2TiO3 were investigated by thermal desorption spectroscopy. The apparent tritium release kinetics of thermal-neutron-irradiated Li2TiO3 was mainly governed by tritium diffusion in Li2TiO3 crystal grains. The irradiation defects and O–D bonds induced in Li2TiO3 by energetic deuterium ion implantation were also investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, respectively. The deuterium release spectra for Li2TiO3 irradiated with energetic deuterium ions consisted of five release peaks. The rate-determining processes for these release peaks were not only deuterium diffusion but also the detrapping of deuterium in irradiation defects and in the dissociation of O–D bonds (hydroxyl groups). The detrapping was the dominant deuterium release mechanism for energetic deuterium ion irradiation because of the shorter diffusion length. The rates of diffusion, detrapping from irradiation defects, and detrapping from hydroxyl groups were determined, and the rate-determining process of hydrogen isotope release in Li2TiO3 crystalline grains of various sizes was assessed.